The research efforts funded by this grant are directed at understanding the way in which the central nervous system controls arm movements. To accomplish this goal we have devised a series of investigations in monkeys and humans. The studies with monkeys will be directed towards ascertaining the role of proprioceptive feedback in arm trajectory formation. We plan to use animals deprived of sensory feedback (dorsal rhizotomy). In humans we will study the arm trajectory around obstacles. In addition, the role and the magnitude of coriolis forces and reactional torques will be studied.